Remove trailing empty element on dependency list

An extra semi-colon had snuck in here which caused the project to be
dependent on a module called "", which of course failed further down
the line.

This error was previously undetected because we didn't have anything
that depended on opm-upscaling.
Detect empty elements in dependency list

These errors are usually an extra trailing semi-colon, which is easy
to put in there for symmetry with the other lines. Give a warning on
this but proceed with the build as usual afterwards.
Merge pull request #224 from rolk/224_findupsc

Fix erroneous trailing empty dependency